82 Caddy- 1.6NA "Bucking" at LOW-MID RPM

[2strokesmoke]

Hi Guys,
I'm Having a problem,with my 82 Caddy,with 1.6 NA diesel.
At low RPM (above idle to approx 2500RPM) I'm getting a bucking or surging. Feels like the engine is missing or stumbleing .
It is more noticable in 1st,2nd and 3rd- Probably dampened in 4th and 5th by the gearing and load.
It is much more noticable under light and moderate throttle.
Seems like heavy throttle,alows engine to power through it,although it is still there.
A little history on the vehicle:
82 Caddy 1.6l NA diesel (original engine) 160,000 miles.
Uses about 1 qt of oil every 500 miles , with only light blowby.
I'm restoring this truck,while using it as my daily driver. Just started driving it about 1 month ago. It has been consistantly delivering 50 MPG and I am easy on it and it cruises easily at 65 MPH on the highway.
While restoring I did the folowing:
Replaced the entire cooling system (everything)
Replaced all belts,hoses ect.
Resealed IP and performed BOTH Gov Mod and advance mod.
Installed 4 reman Injectors and heat sheilds Bosch NA13X,
All new filters (Bosch and Mann)
New Bosch Glow plugs and relay
New Contitech T-Belt and tensioner
Timed the IP to 1.0- double and tripple checked (I have the correct timing tool kit)
Absolutely no Leaks anywhere (Oil or fuel)
No  air bubbles in the clear fuel line at all. I have checked many times with a light behind the line)
It definately feels engine related.
The bucking and Pinging got WORSE ,after installing the reman injectors
Sence I first started driving this truck daily, I have kicked the pump timing back to .90 due to harsh Pinging?
With the pump set at 1.0,the engine was excessively ratteling,even under heavy load,with pinging (as in -sounds like a gas engine preignition ping)while under light load and cruise (very noticable on the highway)Distinctable different from the diesel sounds
With pump at .90 the pinging is gone and low to mid RPM power is better.
But the Bucking still remains
When I did the gov Mod, I shimmed BOTH intermediate and High RPM springs ( I followed the instructions in the wrong gov mod thread) I had assumed that this was the cause of the bucking,when I read the "correct Gov Mod thread"It did mention drivability issues.
So today- I REMOVED the shims on the intermediate spring,while leaving the shims on the high RPM spring.
The result : The bucking is still there,but not as bad (probably because I lost a lot of power and throttle response. Maybe I can regain some of the power,by adjusting the fuel screw?
Sorry for the long winded story - I wanted to give as much info as I could.
I would like to add: The truck was actually fun to drive,with good power and throttle response,with BOTH intermediate and High RPM springs shimmed- I's just the damn Bucking !
Could the Advance Mod be responsible for this ?
Any ideas ? or suggestions? would be greatly appreciated !
Thanks in advance,Mike

[stewardc]

Sounds the same as mine, though mine is a heavily modified 1.9 AAZ turbodiesel.
Define pinging? I don't know mhow anyone could hear this in a diesel.

[8v-of-fury]

I do believe he is trying to define Clack, when he says Ping

Possibly try restoring the springs to stock, and see if the bucking continues? If it does not, then you know it was something you did.

Maybe the extra clack is present to you because you had the pump timed at the stock setting of .90 before? I mean that extra .1 doesn't seem like a lot but its substantial.. and is completely ok for the engine. Did it feel like it had more top end with it at 1.00? as opposed to .90?

[2strokesmoke]

Hi Guys and thanks for your input.
With the IP set at 1.0 the engine pulled harder at higher RPM's,but had poor power at lower RPM's
With IP set at .90 it has good low RPM power and will even pull good from an idle (in 3rd and 4th gears) with much less downshifting. But some High RPM power was sacrificed.
As far as the "pinging" sound:
First : I Have never heard a diesel Ping before. I always thought the clacking was basically preignition and normal.
But believe it or not- this engine was definately making a pinging sound ,while cruising on the highway. It sounded exactly like a gas engine,with harsh pinging from preignition.
An entirely different sound,from the usuall clacking.
If I accelerated hard,or took my foot off the Go pedal,the pinging would go away and returned while at cruise.
I know this sounds  weird. I had a nice size rust hole,in the passenger side kick panel (sence repaired) so I could hear the engine nicely 
 I used to "flip" (buy and sell) diesel rabbits 20 years ago. I advanced IP in the range of 1.0 to 1.10 on dozens of them. This back in the days before the internet  Therefore I have never done a gov mod or advance mod before this vehicle. While I must say,the gov mod is awsome--adding really impresive and much needed power and nicely increasing the RPM range.
I'm wondering if advancing  IP to 1.0 AND doing the "advance mod" as well,might have advanced IP timing too far-resulting in the "pinging" and poor low RPM power.
Agian: the pinging is gone,with pump set at .90
I do still have some light "Bucking" under light and moderate acceleration, between 1500-2500RPM (approx) (NO Tach)
It's just a mild annoyance. I suppose I can't really complain- This truck pulls harder and is MUCH more drivable,than any Rabbit I ever owned  (Including a 1.8 - 8V carb'd rabbit I used to own. I can keep up with traffic on the highway (easily doing 65MPH) and Not hold up traffic,when the light changes to Green. Much better than the Rabbits used to be. If I could eliminate the light bucking, I would be totally satisfied. Agian,thanks to all,for your input and I thank you all for this website. I wish It was available 20 years ago,when I worked on so many of these vehicles. Definately an awsome resource !
Thanks,Mike

[R.O.R-2.0]

is the kill solenoid wire good and tight? my audi anr my rabbit both bucked when the power wire to the stop solenoid was loose, so every time the engine rocked, it would lose contact, then make contact again.. it kinda took me a while to track that one down..

[fatmobile]

All the injection pump mounting bolts tight?
 Even the ones holding brackets to the block?

[2strokesmoke]

Hi, I checked all The IP mounting bolts and bracket bolts - all nice and tight- Thanks,it was a good thought
Stop solinoid wire in tact and tight - another good thought

I just developed a fuel leak today (definately started today,so I don't think it's related)  IP seems to be leaking at fuel distributor mount (where aluminum IP and cast iron Dist meet)
Or so it appears. I brought the truck back home and parked it until this weekend,when I'll have time to check it out.
It figures ! That's the only external seal I didn't replace ! LOL

Update on the "bucking"
It is more pronounced ,before engine is up to full temp (195F)
At full temp it is mild. If I shift early (at low RPM) it won't buck
If I keep the RPM's up high,it won't buck.
Seem to buck between 2000-2500 RPM (approx)
I bucked with IP set at 1.0 and engine clacked under load
It bucks with IP set at .90 and engine is relatively quite under load.
Power output is good.
No air bubbles.
I'm wondering if it could be a fuel supply problem.
I remember reading,that several guys installed a small electric booster pump,near the fuel tank,in the Caddys.
I just don't remember why.
I know all my hoses are good and all connections tight.
I tested the fuel tank vent and it's good too (I bypassed the rollover valve) All hoses at the tank are new as well.
I'm thinking-perhaps the IP is having a difficult time drawing fuel from the tank.
Maybe I'll try installing a booster  pump,just to eliminate that possibility.
Thanks agian,for your input !  Mike

[fatmobile]

A dash-mounted vacuum gauge connected to the fuel line will help you troubleshoot fuel supply problems in the future.
 
If the injection pump is having a hard time pulling fuel,
for many reasons,
 the gauge will let you know way before you are stalled beside the road.

 If there isn't a problem at higher RPMs/loads, it might not be a fuel supply problem.
 
 Might not help but bump up or down the max fuel screw and adjust the idle screw see if it changes anything.

 I had a surge/buck at about that RPM in my TD Golf.

 After a governor mod,
 replaced the short spring with a 1/16" thick washer,
 the power band smoothed right out.

[vako]

I  have the same problem for over two years now  (( new air liter, new lifyers, rebuilt engine and resealed ip pump (but i have never removed delivery valves). New timing belt , tensioned just right, fuel pump set somwhere near .90 (but retarding or advancing static timing does not afect the bucking much. Even messing with internal pressure valve did not help.

Today i ran the engine from fuel canister (to exclude fule line restriction), also ran it woth wastegate stuck open (to exclude faulty wastegate pressure surging) but it still ran the same...
 My engine is 1.9 aaz
Has anyone found any solution for this problem?

[vako]

This is my thread and i have changed the lifters since my last post, but almost nothing changed (despite the fact that one lifter was collapsed and it. Knocked like crazy. I had  only some light improvement in idle smootheness).  http://www.vwdiesel.net/forum/index.php?topic=34128.0

[vako]

P.s. it does it on acceleration and deceleration on the same rpms